Tandem piston filer/sander tool



States tent Inventor Kenneth A. Mclllenry Clinton, New York Appl. No.772,512

Filed Nov. 1, 1968 Patented Oct. 27, 197 0 Assignee Chicago PneumaticTool Corny New York, New York a corporation of New Jersey TANDEM PISTONFlLER/SANDER TOOL 4 Claims, 6 Drawing Figs.

US. Cl 91/309, 91/313,91/329, 51/170.3,173/170 Int. Cl F011 25/06, F01115/18 Field of Search ..91/ 179 (Cursory), 304,, 329, 309, 313:(1nquiredpurser) 173; 51/1703 (Cursory) References Cited UNITED STATES PATENTS1,243,199 10/1917 Miller 91/329 2,333,316 11/1943 Klossner 91/304 2/1953Sprague et al 9l/304 Primary ExaminerPaul E. Maslousky AttorneyStephenJ. Rudy ABSTRACT: A pneumatically powered reciprocating tool havingutilization in various fields, but finding special use in the automotiveindustry as a surface working tool. It includes a housing havingappropriate hand grips for maneuvering the tool. The housing supports atool carrier-plate adapted to accommodate a reciprocable tool, such as afiler or sandpaper carrier. The carrier-plate is reciprocable by meansof a pair of pneumatically operable pistons axially coupled in tandemrelation so as to move in unison. Operating air is fed to the toolthrough a manipulative throttle valve and is caused to be ap pliedalternately to a pair of opposed end faces of the pistons by means of apneumatically shiftable distributing valve. The latter is caused to beshifted for this purpose by means of a pushrod valve which moves as aunit with the pistons. Reciprocation of the pistons and, as aconsequence of the carrierplate, and automatic operation of thedistributing and pushrod valves continues until the operator releasesthe throttle valve to closed condition.

Patented Oct. 27, 1970 Sheet 1 of 2 ATTORN EY TANDEM PISTON FILER/SANDERTOOL BACKGROUND OF THE INVENTION This invention relates to the art ofreciprocating surface working tools of a type driven by means of a pairof pneumatically operable pistons.

The general object of the present invention is to provide areciprocating surface working tool having a simplified operatingmechanism in which a pair of tandem pistons are alternatelypneumatically operable to reciprocate a tool carrier-plate.

A particular feature of the tool of the present invention is itssimplified mechanism in which the application of pneumatic operatingfluid is automatically applied, upon operation of a throttle valve,alternately to each of the pistons as long as the throttle valve is heldopen.

Another special feature of the tool lies in the tandem arrangement ofits reciprocating pistons as well as in the arrangement of a pair ofvalves which operate automatically as a consequence of movement of thepistons to cause application of operating air alternately to thepistons. The tandem ar rangement of the pistons enables both pistons tomove in unison as operating air is applied to one or the other of them.This arrangement enables a simplified housing to be used having adesirable narrow structure.

The particular arrangement of the valves and pistons has a furtherdistinct advantage in that the tool has a positive and immediatestarting operation regardless of the last stopped position of thepistons.

SUMMARY OF THE INVENTION In accordance with the invention. there isprovided a pneumatically powered surface working tool comprising a pairof axially aligned piston chambers, a partition block separating thechambers from one another, a separate piston reciprocable in eachchamber, a surface working tool carrier-plate having its longitudinalaxis parallel to the line of travel of the pistons, means coupling thepistons in tandem relation with each other and to the carrier-plate formovement of the pistons and carrier-plate in unison, a distributingvalve pneumatically shiftable to cause operating air flow alternately tothe piston chambers, and a push-rod valve having movement as a unit withthe pistons controlling pneumatic shifting of the distributing valve.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a view in longitudinal section of a tandem piston pneumaticsurface working tool embodying the invention;

FIG. 2 is a bottom plan view of FIG. 1;

FIG. 3 is a left or front end view of FIG. 1 with some parts brokenaway:

FIG. 4 is a schematic view showing the mechanism of the tool in its laststopped condition, in which condition the pistons have stopped aboutmidway of their stroke to the right;

FIG. 5 is a schematic view showing the pistons at the end of theirstroke to the right, and showing the distributing valve in a shiftedposition preparatory to causing application of live air to the leftpiston member to efi'ect a leftward stroke of the pistons; and

FIG. 6 is a schematic view showing the pistons at the end of theirleftward stroke and showing the distributing valve in a shifted positionpreparatory to causing application of live air to the right pistonmember to effect a rightward stroke of the pistons.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT In the accompanyingdrawings is disclosed a pneumatically powered reciprocating surfaceworking tool. It includeds an elongated housing 11 having a mainhand-grip 12 bolted upon its rearward area and having an auxiliaryhand-grip 13 mounted upon its forward area. A manipulative throttlevalve 14 is incorporated in the housing. The valve is operable to feedoperating air from a live air supply connected inlet 15 to piston andvalve mechanism 16 incorporated in the body of the housing to causereciprocation of a tool carrier-plate 17 located externally at thebottom of the housing. An abrasive tool, such as a file 18, is shownbolted to the underside of the carrier-plate. It is understood that asandpaper carrier (not shown) or other appropriate reciprocableoperating tool may be selectively affixed to the carrier-plate 17 inlieu of the file 18.

Angle or L-brackets l9 bolted to opposite sides of the housing haveinturned legs 21 upon which a pair of longitudinally extending ofisetshoulders 22 of the carrier-plate are supported as the carrier-plate isrelatively reciprocated. The housing has a flat bottomed surface 23 tothe forward area of which is bolted a pair of parallel guide blocks 24,which blocks are separated from one another by a space defining alongitudinal track 25 for guiding a forward pilot member 26 of thecarrier-plate. A second pair of guide blocks 20 is similarly bolted tothe rear underface of the housing, and provides a similar track 27 for arear pilot member 28 of the carrierplate. Tracks 24 and 27 are axiallyaligned. The forward pilot member 26 is of L-form having one leg rivetedto the top forward surface of the carrier-plate and slidable in thetrack 25. An upright leg 31 of the pilot member projects with a slidefit through a longitudinal bottom slot 32 of the housing into theforward area of a forward piston chamber 33. The other pilot member 28,also of L-form has a leg riveted to the top rear surface of thecarrier-plate and is slidable in track 27. It also has an upright leg 35projecting with a slide fit through a rear longitudinal bottom slot 36of the housing into the rear area of a rear piston chamber 37. Pistonchambers 33 and 37 are axially aligned.

A pair of axially aligned pistons 38, 39, is arranged in the housing.The pistons 38 and 39, respectively operable in the forward and rearpiston chambers, are coupled in tandem relation and are reciprocable inunison to transmit reciprocating movement through the pilot members 26and 28 to the carri er-plate 17. Each piston has a bossed end 21abutting the inner face of the upright leg of the corresponding pilotmember. A push-rod valve 42 having longitudinal sliding operation in avalve block 43 separating the piston chambers has one end projectinginto the forward piston chamber 33 that abuts at all times an opposedface of piston 38. The opposite end of valve 42 projects into the rearpiston chamber 37 and at all times abuts the opposed face of the rearpiston 39. In this arrangement, the push-rod valve 42 maintains bothpistons at all times in fixed axial spaced relationship to one anotherand in abutment with the pilot members 26 and 28.

An air distributing spool valve 46 is pneumatically shiftable back andforth in the valve block 43 to cause feeding of inlet air alternately tothe piston chambers. As best seen in the schematic showing of FIG. 4,the distributing valve 46 has obtained a shifted position in which itpermits flow of inlet air to the rear piston chamber 37 to drive therear piston 39 and, as a consequence, the carrier-plate l7 rearwardly tothe right. The distributing valve 46 has a reversely shifted position,as best seen in FIG. 5, in which it permits flow of inlet air to theforward piston chamber 33 to drive the forward piston 38 and, as aconsequence, the carrier-plate forwardly to the left. As each piston ispneumatically driven, it acts through the pilot members 26 and 28 andthrough the connecting carrier-plate I7 to draw the other pistontogether with the pushrod valve 42 along with it.

The pushrod valve 42 controls pneumatic shifting of the distributingvalve. It moves in unison with the pistons. As it moves, it controlsalternate application of inlet air and exhaust to the left end 62 of thedistributing valve 46 to effect shifting of the latter from one positionto the other.

A particular advantage of the tool, as will be brought out later hereinin a summary of its operation, is that its piston and valve mechanism 16will start operating immediately upon application to it of inlet air,regardless of its last stopped condition. The tool does not requireshaking or maneuvering in any manner to reposition its valves or pistonsto enable it to commence operating.

In summary of the operation of the tool, reference is now directedparticularly to the several schematic views of FIGS. 4-6. When laststopped, the piston and valve mechanism 16 of the tool obtained thecondition shown in FIG. 4. Operation of the the tool is begun bymanipulating the throttle valve 14 to open condition; and operation ofthe tool continues automaticaily as long as the throttle valve remainsopen. In FIG. 4, the distributing valve 46 is positioned at the left endof its chamber in abutment with an end stop 47; and the pistons aremidway of their stroke toward the right or rearward direction. Air fromthe inlet passage 10, which is connected with the throttle valve 14, nowenters the distributing valve chamber over branch passages 49 and 50 toapply pressure against the lands 51, 52, and 53, causing the valve toremain pneumatically unbalanced in its left position. The vent 66 servesto subject the small diameter end of the distributing valve toatmosphere pressure. Inlet air now flowing to the right end of thedistributing valve chamber flows over a passage 54 to move piston 39 tothe right. The carrier-plate l7. piston 38 and pushrod 42 follow inunison the movement of piston 39. Air trapped in the left or forwardpiston chamber 33 is exhausted over a passage 55 communicating at thistime around an annulus 56 of the distributing valve with an exhaustpassage 57. After a predetermined extent of movement of the piston 39 tothe right, an annulus 58 of the pushrod 42 uncovers and communicates apassage 59 with a passage 61 to cause application of inlet air to theleft end 62 of the distributing valve. This pneumatically unbalances thedistributing valve causing it to shift to its right position in abutmentwith the stop 63, as in FIG. 5, and the piston stroke or movement of thepistons toward the right then stops in the FIG. position.

In the FIG. 5 position the shifted distributing valve now communicatesthe passage 54 from the piston chamber 37 around the annulus 56 withexhaust passage 57 and connects passage 55 from the left piston chamber33 around the annulus 64 with the branch inlet passage 49. Inlet air nowbeing applied over the branch passage 49 forces the forward or leftpiston 38 to the left causing the carrier-plate 17, the right or rearpiston 39 and the pushrod 42 to move to the left in unison with it.After a predetermined extent of movement of the pushrod to the left, asindicated in FIG. 6, the annulus 58 of the pushrod 42 uncovers andcommunicates the passage 61 with exhaust passage 65 to allow airpressure at the left end of the distributing valve 62 to escape. Thedistributing valve accordingly becomes pneumatically unbalanced in aleftward direction and is forced to its position at the left end of itschamber in abutment with the stop 47, as in FIG. 6. As a consequence ofthe distributing valve shifting to the left, the passage 55 from theleft piston chamber 33 is connected by annulus 56 to exhaust 57, and theright piston chamber 37 is again connected over the passage 54 with theinlet branch 50 causing termination of the piston stroke to the left.This shifting of the distributing valve 46 and consequent reciprocationof the pistons 38 and 39 continues automatically until the operatorreleases the throttle valve to closed condition.

It is to be noted that here the piston chambers 33 and 37 are defined bymeans of a bore extending axially through the housing 11, intermediatelyof the ends of which bore the partition block 43 is tightly fitted. Theopposite ends of the bore are respectively headed by means of aremovable cap 67 and an end portion of handgrip 12.

I claim:

1. A pneumatically powered surface working tool comprising a housinghaving a pair of axially aligned piston chambers, a valve blockcontained entirely within the housing partitioning the chambers from oneanother, a separate piston reciprocable axially in each chamber, asurface working tool carrier-plate having its longitudinal axis parallelto the line of travel of the pistons, means coupling the pistons intandem relation with each other to the carrier plate for reciprdcationof both pistons and earner-plate in unison and for restraining thecarrier-plate against angular movement, a distributing valve within thevalve block pneumatically shiftable to cause operating air flowalternately to the piston chambers, and a pushrod valve in the valveblock having movement as a unit concurrently with both pistonscontrolling pneumatic shifting of the distributing valve.

2. A pneumatically powered surface working tool comprising a housinghaving a pair of axially aligned piston chambers, a partition blockintermediately of the housing spacing the chambers from one another, aseparate piston reciprocable in each chamber, a surface working toolcarrier-plate located externally of the housing having its longitudinalaxis parallel to the line of travel of the pistons, means coupling thepistons in tandem relation to each other to the carrier-plate forreciprocation of both pistons and the carrier-plate for reciprocation ofboth pistons and the carrier-plate as a unit, an operating air supplyinlet passage in the housing, and valve means arranged in the partitionblock having communication with the inlet passage for causing flow ofoperating air alternately to the piston chambers, wherein the pistonchambers are defined by portions of a bore which extends axially throughthe housing, the partition block is fitted intermediately of the ends ofthe bore, a removable cap heads one end of the bore. and a removablehandle heads the opposite end of the bore.

3. A pneumatically powered surface working tool as in claim 2, whereinthe coupling means includes a bracket mounted to one end of thecarrier-plate and projecting through a longitudinal slot of the housinginto the v piston chamber into engagement with one of the pistons. asecond bracket mounted to an opposite end of the carrier-plateprojecting through a second longitudinal slot of the housing into theother piston chamber into engagement with the other piston, and apushrod slidable in the block maintaining the pistons in a fixed axiallyspaced relation to each other.

4. A pneumatically powered surface working tool comprising a pair ofaxially aligned piston chambers, a valve block partitioning the chambersfrom one another, a separate piston reciprocable in each chamber, asurface working tool carrierplate having its longitudinal axis parallelto the line of travel of the pistons, means coupling the pistons intandem relation with each other to the carrier-plate for reciprocationof both pistons and carrier-plate in unison, and a distributing valvewithin the block pneumatically shiftable to cause operating air flowalternately to the piston chambers, the coupling means including apushrod valve controlling pneumatic shifting of the distributing valve,the pushrod valve being axially slidable in the partition block andhaving its ends at all times in abutment with opposed inner faces of thepistons, and a pair of brackets each fixed to an opposite end area ofthe carrierplate and each bracket being at all times in abutment withthe outer end face of a separate one of the pistons.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 35,983Dated t er 27, 1970 Kenneth A. McHenry Inventor(s) It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shovm below:

Column 1, line 72, "includeds" should read includes Column 3 line 8, "ofthe the tool" should read of the tool line 54, "inlet branch 50" shouldread inlet branch passage 50 Column 4, lines 27 and 28, cancel "forreciprocation of both pistons and the carrier-plate".

Signed and sealed this 20th day of April 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents USCOMM-DC 003764 59 FORM PO-IOSD (10-69) us,r-ovnuuzm rnm'rmc ornc: 1 an mun-an

